From: Marcus Comstedt <marcus@mc.pp.se>
Date: Sat, 19 Jul 2014 08:04:19 +0000 (+0200)
Subject: View: Implement pinch-zoom
X-Git-Url: http://git.code-monkey.de/?p=pulseview.git;a=commitdiff_plain;h=4b4f1c0dc17b481b798e60bbc3fa639c09a9c788

View: Implement pinch-zoom

The special handling of a moveMoveEvent without a preceeding
mousePressEvent is a workaround for an issue where you won't get
an emulated mousePressEvent for the primary touch after a multitouch
gesture where you release the primary touch before the secondary touch.
---

diff --git a/pv/view/view.cpp b/pv/view/view.cpp
index 392114c..1d55e14 100644
--- a/pv/view/view.cpp
+++ b/pv/view/view.cpp
@@ -469,6 +469,9 @@ bool View::viewportEvent(QEvent *e)
 	case QEvent::MouseButtonDblClick:
 	case QEvent::MouseMove:
 	case QEvent::Wheel:
+	case QEvent::TouchBegin:
+	case QEvent::TouchUpdate:
+	case QEvent::TouchEnd:
 		return false;
 
 	default:
diff --git a/pv/view/viewport.cpp b/pv/view/viewport.cpp
index c578963..9f60c1a 100644
--- a/pv/view/viewport.cpp
+++ b/pv/view/viewport.cpp
@@ -38,8 +38,12 @@ namespace view {
 
 Viewport::Viewport(View &parent) :
 	QWidget(&parent),
-        _view(parent)
+        _view(parent),
+	_mouse_down_valid(false),
+	_pinch_zoom_active(false)
 {
+	setAttribute(Qt::WA_AcceptTouchEvents, true);
+
 	setMouseTracking(true);
 	setAutoFillBackground(true);
 	setBackgroundRole(QPalette::Base);
@@ -96,12 +100,43 @@ void Viewport::paintEvent(QPaintEvent*)
 	p.end();
 }
 
+bool Viewport::event(QEvent *event)
+{
+	switch(event->type()) {
+	case QEvent::TouchBegin:
+	case QEvent::TouchUpdate:
+	case QEvent::TouchEnd:
+		if (touchEvent(static_cast<QTouchEvent *>(event)))
+			return true;
+		break;
+
+	default:
+		break;
+	}
+
+	return QWidget::event(event);
+}
+
 void Viewport::mousePressEvent(QMouseEvent *event)
 {
 	assert(event);
 
-	_mouse_down_point = event->pos();
-	_mouse_down_offset = _view.offset();
+	if (event->button() == Qt::LeftButton)
+	{
+		_mouse_down_point = event->pos();
+		_mouse_down_offset = _view.offset();
+		_mouse_down_valid = true;
+	}
+}
+
+void Viewport::mouseReleaseEvent(QMouseEvent *event)
+{
+	assert(event);
+
+	if (event->button() == Qt::LeftButton)
+	{
+		_mouse_down_valid = false;
+	}
 }
 
 void Viewport::mouseMoveEvent(QMouseEvent *event)
@@ -110,6 +145,12 @@ void Viewport::mouseMoveEvent(QMouseEvent *event)
 
 	if (event->buttons() & Qt::LeftButton)
 	{
+		if (! _mouse_down_valid) {
+			_mouse_down_point = event->pos();
+			_mouse_down_offset = _view.offset();
+			_mouse_down_valid = true;
+		}
+
 		_view.set_scale_offset(_view.scale(),
 			_mouse_down_offset +
 			(_mouse_down_point - event->pos()).x() *
@@ -142,6 +183,53 @@ void Viewport::wheelEvent(QWheelEvent *event)
 	}
 }
 
+bool Viewport::touchEvent(QTouchEvent *event)
+{
+	QList<QTouchEvent::TouchPoint> touchPoints = event->touchPoints();
+
+	if (touchPoints.count() != 2) {
+		_pinch_zoom_active = false;
+		return false;
+	}
+
+	const QTouchEvent::TouchPoint &touchPoint0 = touchPoints.first();
+	const QTouchEvent::TouchPoint &touchPoint1 = touchPoints.last();
+
+	if (!_pinch_zoom_active ||
+	    (event->touchPointStates() & Qt::TouchPointPressed)) {
+		_pinch_offset0 = _view.offset() + _view.scale() * touchPoint0.pos().x();
+		_pinch_offset1 = _view.offset() + _view.scale() * touchPoint1.pos().x();
+		_pinch_zoom_active = true;
+	}
+
+	double w = touchPoint1.pos().x() - touchPoint0.pos().x();
+	if (abs(w) >= 1.0) {
+		double scale = (_pinch_offset1 - _pinch_offset0) / w;
+		if (scale < 0)
+			scale = -scale;
+		double offset = _pinch_offset0 - touchPoint0.pos().x() * scale;
+		if (scale > 0)
+			_view.set_scale_offset(scale, offset);
+	}
+
+	if (event->touchPointStates() & Qt::TouchPointReleased) {
+		_pinch_zoom_active = false;
+
+		if (touchPoint0.state() & Qt::TouchPointReleased) {
+			// Primary touch released
+			_mouse_down_valid = false;
+		} else {
+			// Update the mouse down fields so that continued
+			// dragging with the primary touch will work correctly
+			_mouse_down_point = touchPoint0.pos().toPoint();
+			_mouse_down_offset = _view.offset();
+			_mouse_down_valid = true;
+		}
+	}
+
+	return true;
+}
+
 void Viewport::on_signals_changed()
 {
 	const vector< shared_ptr<Trace> > traces(_view.get_traces());
diff --git a/pv/view/viewport.h b/pv/view/viewport.h
index 0474b7e..f7c8028 100644
--- a/pv/view/viewport.h
+++ b/pv/view/viewport.h
@@ -23,6 +23,7 @@
 
 #include <QTimer>
 #include <QWidget>
+#include <QTouchEvent>
 
 class QPainter;
 class QPaintEvent;
@@ -46,10 +47,13 @@ protected:
 	void paintEvent(QPaintEvent *event);
 
 private:
+	bool event(QEvent *event);
 	void mousePressEvent(QMouseEvent *event);
+	void mouseReleaseEvent(QMouseEvent *event);
 	void mouseMoveEvent(QMouseEvent *event);
 	void mouseDoubleClickEvent(QMouseEvent * event);
 	void wheelEvent(QWheelEvent *event);
+	bool touchEvent(QTouchEvent *e);
 
 private slots:
 	void on_signals_changed();
@@ -60,6 +64,11 @@ private:
 
 	QPoint _mouse_down_point;
 	double _mouse_down_offset;
+	bool _mouse_down_valid;
+
+	double _pinch_offset0;
+	double _pinch_offset1;
+	bool _pinch_zoom_active;
 };
 
 } // namespace view